Art of planographic printing



Patented Feb. 29, 1944 ART OF PLANOGRAPHIC PRINTING William B. Wescott, Dover, Mass" asslgnor to Addressograph-Multimph Corporation, Wilmlngton, DeL, a corporation of Delaware No Drawing. Application January 4, 1940,

- Serial No. 312,391

16 Claims. (Cl. 101-1492) This invention relates to an improvement in the artof planographic printing and it comprises directly delineating on a dry cellulosic printing surface a printing image with a water-immiscible material which is sp ntaneously sorptive by said gagainst theattritional effects of the dampening and inking operations of planographic printing and it also comprises an image-forming material which is spontaneously sorptive for the printing surface and ,is preferentially ink-receptive and persistently retentive of printing ink contacted therewith against the attritional forces inherent in planographic printing operations, said imageformer being chosen from the groups hereinafter listed and being either a material directly applicable to the printing surface or a composition capable of leaving thereon a substantially waterimmiscible residue exhibiting such properties; and it further comprises the method of delineating the image by subjecting the residue of the composition on the printing surface to selective ultraviolet irradiation, and it also comprises the combination of a planographic printing plate having a celluthe plate have thereafter been treated to render them preferentially water-wettable, if the greasy image-forming material be then removed by a solvent and the entire surface of the plate dampened with water, it will be found, upon the application of ink thereto in the usual manner, that the ink will displace water from, and will adhere only to, such .portions of the plate as were originally covered by thegreasy image-forming material and that the plate will print as though the original image-forming material had not been disturbed.

The persistence of a printing image directly delineated upon the surface of a usual zinc planographic plate is thus due to a modification of the plate surface whereby the image area is rendered preferentially and highl grease-receptive, and is not dependent upon the retention of the original image-forming material upon the image area. Indeed, it is the usual procedure with metal plates, after washing out of the original fatty acid image material subsequent to the rendering lyophilic of losic printing face comprising a unifying nonfibrous continuum of substantially pure cellulose characterized by a low lateral water-diffusion rate with an image delineated thereon by such image former: all asmore fully hereinafter described and claimed.

The art of planograpnic printing depends, as

does the older 'art of lithographic printing, upon face of absorbent stone and the younger related planographic process has heretofore made use of variously-treated metal surfaces.

In these prior processes the imageis directly delineated upon the plate by greasy material com- 1 prising a free fatty acid, and its retention thereby depends preponderantly upon a chemical reaction .between the printing surface thereof and the fatty acid constituent of the greasy image-forming material. That such-a reaction takes place is demonstrated by the fact that, after the greasy image has been directly applied to a zinc plate for instance, and after the non-image portions of image-forming material in a physically intact condition upon the image area. There is not, as with a zinc plate, any substantial modification of the cellulosic substance of the printing surface by chemical reaction of the free fatty acid component of the usual greasy image-forming material therewith, since the removal by solvent of the said material from the printing surface of a cellulosic plate and the subsequent dampening thereof completely destroys the preferential grease-wettability or ink-receptivity of what were the image areas of said surface, thus demonstrating that the free fatty acid component of usual greasy image-forming materials does not have that reaction with said cellulosic substance upon which.

the retention of direct-images by zinc plates or stone depends, and that, contrary to the essence of lithographic or metal planographic practice, free fatty acid is neither an essential nor-as will hereinafter appear-a desirable constituent of direct-image-forming materials upon cellulosic printing plates.

While usual image-forming materials compriswhen moist, are ink-repellent-the image-forming material not having in any substantial way modified the plate surface as would have been the case if the plate were of stone or zinc.

In order to lengthen the printing life of a greasy image upon a cellulosic plate, I have directed in my United States Patent No. 2,134,165, dated October 25, 1938, the integration of such an image with the cellulosic substance of the printing face of said plate by heating it or by allowing it to remain on said surface for an appreciable length of time (several hours or more) before proceeding with the printing operation. This treatment, however, takes t me and delays the operator since it is not feasible to use the plate in planographic printing as soon as the image has been applied, as is often desired.

A further and greater objection to this treatment is that the integration with a cellulosic printing surface of greasy image-forming materials by heat or time coincidentally tends to set" or integrate therewith finger marks or other greasy accidental or adventitious smears, and it is an advantage of the discovery upon which this invention is based that, immediately after the delineation of the image upon a suitable cellulosic printing surface with image-forming material of the type hereinafter set forth orwhen the said materials comprise a volatile component or vehicle-immediately after the evaporation of said component or vehicle, the said surface may be dampened with water or preferably with an acidic dampening solution such as is described in my Patent No. 2,003,268, whereby the non-image areas thereof are rendered ink-repellent and the ink-receptiveness of adventitious greasy smears, finger marks and the like thereon, if of recent origin and not integrated by heat or long contact therewith, is substantially negatived and the said non-image areas then, 'or at most after a few passes of the inking and dampening rollers thereover, will refuse ink and remain free from ink scum so long as they are adequately dampened during printing.

I have now further discovered that the retention of direct image-forming material by unified cellulosic surfaces under printing conditions is determined by the sorptive bond or physical adhesion thereof to the cellulosic material and that, in place of the usual greasy image-forming materials, certain materials of the types hereinafter described and when directly impressed on plates having a unified cellulosic printing surface are capable of yielding a substantially longer imagelife under printing conditions than has been heretofore obtainable under like modes of image application and like printing conditions. Furthermore, such materials have been found to exhibit a spontaneously sorptive bond for unified cellulose and hence a plate having a unified cellulosic face imaged therewith can be advantageously used in planographic printing without such delay as is required to integrate usual greasy image-forming materials with cellulosic printing surfaces. In addition, an image delineated on a unified cellulosic printing surface with such spontaneously sorptive material possesses greater resistance to displacement therefrom by the forces incident to printing than one applied thereto with usual greasy material even though the latter be integrated therewith by heat or time; which is of advantage.

In my copending application Serial No. 312,390, filed January 4, 1940 I have described unified cellulosic surfaces characterized by a low lateral water-diffusion rate; and I have further discovered as part of this invention that the spontan'eous sorptivity of the hereinafter-described materials and their resistance to displacement by dampening fluids under printing conditions is greater for unified cellulosic surfaces characterized by a low lateral water-diffusion rate than for otherwise like surfaces having a high lateral water-diffusion rate.

This discovery provides a method of pianographic printing from unified cellulosic plates, preferably having a low lateral water-diffusion rate, wherein such plates are prepared for printing by the direct-image delineation upon the substantially water-immiscible and is preferentially wettable by usual lithographic ink, whereby substantially longer editions are obtainable by direct or offset planographic printing than can be obtained under otherwise like conditions by like means from usual greasy image-forming materials similarly applied to such plates. It further provides in combination a printing plate faced with a unified cellulosic material preferably having a low lateral water-diffusion rate and prepared for planographic printing and a printing image portion consisting of image-forming material which is spontaneously sorptive by said cellulosic material, substantially water-immiscible. preferentially wettable by usual greasy lithographic printing inks applied in the usual way and persistently adherent to said cellulosic material against the attritional effects of the usual planographio dampening and inking operations. It also provides an image-forming material, adapted to direct delineation upon the unified cellulosic printing surface of a planographic printing plate, which material is spontaneously sorptive by said surface, is physically retained substantially intact over the delineated image area, is water-immiscible, and is preferentially ink-wettable; and its adhesion to said face, persisting when the latter is subsequently saturated by an aqueous dampening fluid, and its internal cohesion and its adhesion to printing ink are severally substantially greater than is the internal cohesion of a usual lithographic printing ink suitable for use therewith, in direct or offset planographic printing.

In general the spontaneous sorptivity by unified cellulosic surfaces of image-forming materials of the type hereinafter described, and the resistance of said materials to displacement from said surfaces, by the combined effects of dampening fiuids applied thereto and printing ink rolled thereover under printing conditions, are great in some measure of inverse proportionality as the free fatty acid content of said materials and the lateral water-diffusion rate of the substance of said surfaces are both diminishingly low.

many materials comprising free fatty acids, which normally either exhibit no image-forming characteristics at all or do so to such a slight extent as to render them substantially without utility for the present purposes, may be so modified in various ways as to greatly reduce or completely eliminate the free fatty acid content thereof and coincidentally so improve their image-forming abilities as to provide that spontaneous sorptivity which characterizes the image-forming materials of this invention.

I have further discovered that certain potential spontaneously-sorptlve image-forming materials which are normally incapable of forming a printing image may be rendered ink-receptive and -retentive by means of ultraviolet irradiation. This discovery provides a method of preparing cellulosic plates for planographic printing from direct images photogenically produced thereon by the action of ultraviolet irradiation upon a photosensitive potential image-forming material thinly spread over the printing surface or a portion of the printing surface of said plates, whereby the said photosensitive material in, and only in, the

irradiated areas-which may. be, and conveniently are, determined by a negative transparency-is rendered preferentially ink-wettable and retentive of printing ink against the attritional effects of the usual dampening and printing operations and whereby the non-printing areas, notwithstanding the presence thereon of the said potential image-forming material, remain preferentially water-wettable and'require no more than the usual dampening operation to become ink repellent.

It also provides a method of preparation of cellulosic plates for planographic printing which consists solely in directly delineating, on the printing face thereof, an image with a spontaneously-sorptive image-forming material of I the character hereinafter described, dampening the said face and rolling lithographic ink thereover whereby to selectively ink said image.

It is an advantage of this discovery that the printing life of an image, when directly delineated with such spontaneously-sorptive imageforming materials on cellulosic plates and particularly when the substance of the unified cellulosic surface thereof has a low lateral water-diffusion rate, is substantially greater than that of like images similarly delineated with the usual greasy image-forming materials,.under otherwise like conditions; and it is a further advantage that plates prepared according to this invention will yield long editions even when printed from immediately after delineation and dampening, and without resort to the integrating effect of heat or time, as is required to integrate greasy imageforming materials with cellulosic plates, as set forth in my above-mentioned Patent No. 2,134,165.

For best results, the cellulosic printing plate is first treated according to my copending application Serial No. 312,390, whereby the lateral water-diffusion rate is lowered, so as to be not more than 25 millimeters in 4 hours; and is then, except for the choice of image-forming material, prepared for printing in the following manner: to wit, the hereinafter described imageforming material is directly applied to the dry unified cellulosic printing face of the plate, a preferably acidic dampening solution is subse-' quently applied to the entire area thereof whereby the non-image areas are selectively moistened, and then without further preparatory treatment the ink rollers are passed over said entire surface area and the ink will adhere only to the image areas. Printing is thereafter carried out in the usual direct or offset planographic manner, ex

cept that the usual gumming up operation is avoided and gum arabic is preferably and advantageously omitted from the dampening solution.

In order to have printing utility in the field of office duplication and to be commercially practical, a directly-delineated planographic printing image must be capable of yielding at least one thousand clean facsimile copies without suffering appreciable disintegration or degradation. By this is meant that there should be no gross degradation of the copy at the one-thousandth impression as compared to the first impression. Spontaneously-sorptive image-forming materials having the hereinafter-stated characteristics when applied to suitable cellulosic surfaces of the character described in my copending application Serial No. 161,970, filed September 1, 1937, and in my above-identified copending continuation thereof, Serial No. 312,390, are capable of yielding commercially practical results under planographic printing conditions, and the materials of the preferred examples hereinafter given have been found to yield, under practical offset printing conditions, clean facsimile copies in editions of from two to more than fifteen thousand imipressions.

It is obvious that planographic image-forming materials must vary widely in physical characteristics to meet the requirements of the several variant modes of image delineation. Thus, a crayon composition must be a solid of a wellrecognized character, capable under frictional attrition of leaving tracings of its substance upon the printing surface; while, at the other I extreme, a. writing composition suitable for pen work must be a fluid of suitablylow viscosity and high surface tension to flow readily from the nib or drawing pen and yield a clean fine line, and it must comprise a suitably volatile vehicle. Between these extremes there are several variant types, such as the impregnant for typewriter ribbons which must comprise a stable viscous fluid of very low vapor pressure; transfer inks for delineations by means of stamp forms or other printing elements which require more or less viscous fluids with high or low vapor pressure, depending upon the nature of the image-imprinting procedure; background stippling inks characterized by a low viscosity fluid comprising a highly volatile vehicle, which inks are adapted to spraying or spattering from a brush upon the printing surface; and finally photogenic image-forming materials capable of serving as direct-image-forming materials which must be carried by a volatile vehicle of low viscosity to the end that a uniformly thin layer thereof may be spread over the desired portion of the printing surface.

While it has not been found possible to group under conventional chemical or physical classification the spontaneously-sorptive-image formmaterial types.

The characteristics common to the imageiorming materials of this invention, in terms of the requirements they must fulfill, may be stated as follows: (1) The image-forming material or composition as applied to, or as residual on, the unified cellulosic printing face of a planographic plate must be substantially water-immiscible at least at room temperatures, since otherwise the image would of necessity be impaired by the dampening to which the plate is of necessity subjected before inking and during printing; and the image on the said printing lace must remain physically intact in'the sense that it must maintain a surface coverage over the entire original image area since, as pointed out above, the capacity for reproduction of an image upon a cellulosic printing" face depends soley upon the persistence thereon of the imagefoiming material; (2) The image-forming material or composition must a component which is-or which as the result of suitable treatment may become--preferentially wet 'by, and retentive of, usual lithographic printing ink since a, portion of the printing ink components of the hereinbelow listed coextensive with the image area must be retained thereby, notwithstanding the necessary prior dampening of theplate in its entirety; (3) The image-forming material or composition as applied to, or as residual on, the dry print ing face of the cellulosic plate must firmly and spontaneously bond or adhere thereto, and-'- whether by absorption in, or by adsorption on,

the substance of said printing face-such sorp-' tive bond must, notwithstanding the subsequent dampening of vthe cellulosic substance of said printing face, remain substantially the original image area since age would "work sharp" as the image area decreased or would fatten as the image area increased; and both the internal cohesion of the image-forming material and its sorptive bond to said substance, when the latter is subsequently dampened, must be severally substantially greater than both the adhesion of the said material to, and the internal cohesion of, the printing ink used therewith; and said sorptive bond must offer effective resistance to degradation by the attritional forces brought to bear under printing conditions; (4)"I'he spontaneously-sorptive image-forming material or composition as applied to, or as residual on, the surface of the plate must have substantially greater resistance to displacement therefrom under under printing conditions than have otherwise similar usual greasy image-forming materials under like conditions of application and printing.

More briefly stated, any fluid or plastic composition capable of leaving on a dry cellulosic printing surface a substantially water-immiscible residue thereon, which is preferentially wettable by a lithographic printing ink, which exhibits a spontaneously sorptive cohesion with said surface that persists when the latter is subscquently saturated with aqueous dampening fluid and exhibits an adhesion for said ink greater than the internal cohesion of said ink, and which has a substantially greater resistance to the impairment of its physical integrity and to its displacement from said surface under printing conditions than have otherwise similar usual greasy image-forming materials when similarly applied to like surfaces and under like printing be, or must comprise confined to otherwise the irncellulose and such high sorptive conditions. is deemed to come within the purview of this invention.

To be commercially useful. the life of a pianographic direct-image must be such as to yield an edition of at least one thousand clean facsimile copies, as stated, and for the present purposes the direct-image life of usual greasy image materials on the printing face of cellulosic plates and integrated therewith to prolong their life is, under optimum printing conditions, accepted as an adequate and satisfactory criterion of minimum commercial utility. As previously pointed out, mere contact of the usual greasy image materials with cellulosic printing surfaces does not furnish an image of satisfactory life within the purview of this invention.

Usual greasy image-forming materials generally comprise a component high in free fatty acid to react with the substance of the printing surface, a pigment to renderthe delineation readily visible, .andv commonly one or more components adapted either to increase the water-immiscibility or to increase the'ink-retentiveness or both, and further adapted to, impart to the whole the desired consistency. :Noneof these usual greasy, image-forming materials isspontaneously sorptive" on surfaces of substantially pure unified of them as have utility in connection, with unified cellulosic printing surfaces are useful only-when integrated therewith by heater long contact therewith prior to printing; nevertheless some of them may be so modified by eliminating or greatly reducing the free fatty acid content as to become sufficiently spontaneously sorptive for the present purpose. The composition" of spontaneously-sorptive image-forming materials requires a component which is ink-re- I ceptive and rete'ntive, which component may be such as has been used heretofore for the same purpose in greasy image-forming compositions; and it also requires a component which has a cohesion for unified cellulosic surfaces and particularly for such surfaces having a high oxidation-products content. These components in some instances may be one and the same, although in general the particular requirements of viscosity-or plasticity, as the same may be-are best met by using two or more components complementary to each other in that one may impart the desired high spontaneous sorptivity, another the desired ink-receptivity and -retentiveness and, if required, the third may serve as a transient solvent only or as a permanent vehicle imparting to the whole the desired viscosity or plasticity and the necessary internal cohesion.

Anyone skilled in the art of planographic printing, and particularly offset planographic printing, will appreciate the fact that diminishing returns may obtain when a substantial departure is made in either direction from the optimum printing ink consistency. Thus, if an attempt is made to favor the image material by using a soft buttery printing ink, so much dampening etch is required to keep the background clean that the image tends to be drowned, and "works sharp" and finally disintegrates more rapidly than would obtain under optimum moistening conditions. If, on the other hand and against the dictates of good offset practice, a very stifi and tacky ink is used, the image may fall through want of sufficient internal cohesion to withstand the pull of the ink. A medium stiff, though not buttery, off set lithographlc ink-when used at normal room temperatures-provides a generally satisfactory forth, anyone skilled in the art should-be able to assemble, from the appended list of suitable ingredients, spontanepusly-sorptive image-forming materials to meet the several variant requirements of planographic printing from cellulosic surfaces and to qualify by the hereinbelow-described test, as coming within the purview of this invention.

Because of the manifold variants more or less affecting image-life, such for instance as may exist in printing conditions, in mode of image formation, in the microtexture of unified cellulosic printing surfaces and in the lateral water-diffusion rate thereof, it is not possible to foretell precisely the number of facsimile copies obtainable from a direct-image formed on such surfaces by a particular image-forming material.

I have found, however, that the relative utility of image-forming materials which fulfill the hereinabove-listed requirements and which fall within the purview of this invention may; be readily and expeditiously ascertained by a simple test, which comprises subjecting an image-delineated with one of said materials upon a unified cellulosic printing face-town accelerated attritional action far greater than that incident to normal planographic printing operations. This qualifying test is performed in the following manner: 1) A cellulosic printing plate is chosen of the character described in my above-identified Patent No. 2,134,165 and my copending applications Serial .Nos. 161,970 and 312,390, and particularly characterized by'a printing face composed of substantially pure cellulosic material surfaced and unified by a non-fibrous cellulosic continuum having a lateral watendiifusion ratev in the range of -30 millimeters in 4 hours, as ascertained by the method set forth in said apsuch free fatty acids although and unified by,

the conditions of the above-described qualifying test, survive more than 4 or 5 cyclical attritional re-rollings and an image formed of a standard Korn No. 4 lithographic crayon material, for instance, will not-under the said conditionssurvive the inking passes; but, when the diffusion rate of. the cellulosic surface is so low as'to be in the range of 5-10 millimeters in 4-hours, said crayon material may survive from 2-5 cyclical re-rollings, while the preferred crayon compositions of this invention will-under like circumstances-withstand upwards of fifty such passes.

Usual or greasy image-forming materials are 1 for the present purposes defined as embracing all image-formers as commonly used in planegraphic printing from metal to form a directprinting image (in contrast to'a photographic image) comprising essentially a free fatty acid, a soluble fatty acid soap or a fatty acid ester such as stearin and the vegetable waxes; where- ,as, by contrast, image-formers falling within the purview of this invention should not contain they may comprise an insoluble metal soap, such as a copper, barium, iron, or lead stearate, oleate or other soap, or may comprise an unsaturated fatty oil polymerized by oxidation, irradiation or halogenation as by chlorination for instance.

The expressions image-forming material and image-former, unless qualified by usual, greasy or fatty or unles clearly indicated by the context to embrace both the prior direct-imageformers and those of this invention, are used herein with reference to those materials or compositions which exhibit spontaneous-sorptivity for normally dry cellulosic surfaces comprising or consisting of, a non-fibrous continuum of substantially pure celluloseand which further exhibit, when and as originally applied to and residual as thin deposits on said surfaces'and after subsequent dampening thereplication, Serial No. 312,390; (2) An image is I delineated on the printing face of said plate with the image-forming material under test and in a mode appropriate thereto, and any volatile vehicular component thereof, it such there'be, ir allowed to evaporate at room temperature; (3)

Immediately thereafter said plate is immersed in a bath of the hereinabove-mentioned etch for one minute; (4) Then the image, while still submerged in said bath. is inked up with a medium stiff offset lithographic ink by means of two light cyclical passes thereover of a hand brayer having a soft rubber roller evenly and heavily charged with said ink; (5 The said so-charged brayer is then lightly rolled along a path that is normal of, a preferential ink-wettability and -retentiveness against the attritional displacement thereof from said surfaces by the forces inherent in direct, or oil'set planographic printing under usual printing-conditions.

By the expressions spontaneous sorptivity and spontaneously sorptive as used herein is meant an adhesion or adhesiveness for unified cellulosic printing surfaces, whether by absorption in or adsorptionion said surfaces, which is effected I by more contact of image-formers therewith and without the necessity of heating or a long time to the axis of the brayer so that its progress is one of pure rotation in a direction at right angles to the previous inking passes, in such manner as,

to avoid twisting or skidding the brayer and as to traverse a major portion but not all of the imaged area for 15 cyclical passes, or 30 single passes over said portion of the imaged area; and (6) The inked and re-rolled portions of the imaged areas are visually inspected. If, as a result of this test, there is no gross difference in appearance between the said portions of the imaged area, the image-forming material is considered to be within the purview of this invention.

No known usual greasy image-forming material having a sufilciently high content of free fatty acid to be serviceable as a direct imageformer on a zinc planographic plate will, under interval between such contact and subsequent dampening as is required for normal greasy image-forming materials. v

' By the expression unifying continuum as herein used is meant that non-fibrous form of cellulose resulting from gelatinization, by chemlcal reaction in the case of amyloid parchment and by mechanically accelerated hydration in the case of so-called glassine or greaseproof paper, which continuum not only surrounds the residual fibers as a coating but also serves to unify the whole by contact fusion, thus moreor less completely filling the. interstices and forming a non-fibrous continuum from any part of the structure to any other part thereof.

Another example of a cellulosic continuum is found in a sheet of regenerated cellulose.

By the expression unified cellulosic material is meant any sheet material composed essentially of substantially pure cellulose, thevwet strength of which is primarily dependent upon that of a component non-fibrous continuum which may,

'is submerged for 1 minute 'as in the case of nlmiform regenerated cellulose, be the sole component of material.

By the expression oxidation-products content is meant the total effect of oxidation of the celluiosic component or components of a unified celluiosic material, such as parchment, glassine, greaseproof or regenerated cellulose, as represented by the arbitrary numerical sum of the values obtained for oxycellulose in terms of copper number (expressed in grams) and for hydrocellulose in terms of cold alkali solubility (expressed in percentage) by the more sensitive of the known methods.

The expression planographic printing is used herein, in the commonly accepted sense-which includes rotary offset printing, to denote that printing process in which the surface of the printing plate is substantially plane and in which the printing image is substantially in the plane of the printing surface; that is to say, the printingimage is neither raised appreciably above nor sunk much below the plane of the printin image. p The expression celluiosic printing plate is herein used to denote a celluiosic structure, such as is more fully described in my Patent No. 2,134,165 and my copending application, Serial No. 161,970, characterized by a printing face of substantially pure unified celluiosic material and an integral backing adapted to restrict the swelling of the said printing face to a direction normal thereto when, under printing conditions, said face is dampened.

The expression surface is used herein in a broadly inclusive three-dimensional sense as commonly used, and not in the strictly twodimensional sense as used in scientific reference to molecular surface phenomena, for instance.

For the present purpose the lateral diffusionrate of water in unified celluiosic material is defined as the height (expressed in millimeters) to which distilled water rises in a sheet of said material over a period of 4 hours when the edges thereof are sealed against absorption of water in any convenient manner and when the sheet is suspended over a quiescent bath of said water at room temperature under the following further conditions: (1) the lower end of the sheet is maintained below the level of the bath, this being conveniently accomplished by folding a bit of sheeted block tin over the bottom edge; (2) the machine direction of the sheet is to be parallel to the surface of the bath; (3) the portion of the specimen above the bath is surrounded by moisture-saturated air; (4) a marker having been inscribed at the edge of the sheet, the sheet to exactly this mark and then raised by an amount slightly greater than the expansibility of the sheet in a direction normal to the machine direction thereof; (5) the sheet isv suspended thus for 4 hours, at the end of which time the rise from the marker is measured off in millimeters.

By the expression irradiation as herein used is meant irradiation with ultraviolet light at an at a distance and for a time sufllcient to bring about the desired change in the substance being treated. For very thin deposits of photogenically potential image-formers, such as certain pitches and unsaturated vegetable oils, on celluiosic printing surfaces an irradiation from a mercury vapor arc lamp (Haenergy output and novia type) at a mean distance of ten inches for,

the unified celluiosic 15-30 minutes sufllces to render such potential image-formers ink-receptive.

The expressions free fatty acid, greasy or fatty are herein used to embrace th essential fatty acid component of usual image-formers required for direct-image delineation on zinc and stone for planographic printing, which component comprises essentially a free fatty acid, a soluble fatty acid soap or a fatty acid ester such as stearin and vegetable waxes; but they do not embrace such acids as are comprised in an insoluble metal soap such as copper, barium, iron or lead stearate. oleate or other soap, or such acids when polymerized by oxidation, irradiation or halogenation as by chlorination for instance.

The objectionable eflect of the inclusion of free fatty acid in an image-former when used on celluiosic printing surfaces may be made qualitatively manifest by drawing a set of lines on a celluiosic printing surface with a one per centum solution of abietic acid in acetone, another set of lines with a one per centum solution of oleic acid in acetone, and a third set of lines with a solution of one-half per centum abietic acid and onehalf per centum oleic acid in acetone; and, after the evaporation of the acetone, by exposing a portion of each of the three said sets of lines to irradiation by ultraviolet light for 15 to 30 minsets of lines delineated with oleic acid alone and with abietic and oleic acids together do not acl cept ink in the unirradiated portion at all and in the irradiated portion the oleic acid has become slightly ink-receptive while the abietic acid 'admixed with oleic acid has suffered so great a loss of ink-receptivity as to be but little better than the irradiated oleic acid alone.

When a celluiosic printing surface which is not composed of substantially pure cellulose but contains substantially more than spectroscopic amounts of metal salts, as copper sulphate for instance, or comprises siliceous material in its surface finish, is imaged with usual greasy image forming materials, theresistance of that image to attritional disintegration may approach that of images formed on substantially pure unified celluiosic surfaces by the spontaneously-sorptive image-forming materials of this invention; but the presence of metal salts or siliceous materials in the substance or on the printing surface of celluiosic plate materials in suilicient amount to substantially improve the performance of usual greasy image-forming materials thereon is deemed to remove said plate from the class of celluiosic plates as herein elsewhere defined. Which is not to say that the spontaneously-somtive image-forming materials of this invention arenot of utility on celluiosic plates modified by component metal salts or siliceous materials, but only to say that a particular merit of the image-forming materials of this invention is in the substantial advantage derived from the use of said materials in combination with printing plate faces composed of substantially pure unified cellulose, and particularly when said cellulose has a high oxidation-products content, over the use with like printing faces of usual greasy imageforming materials.

Spontaneously sorptive image-forming materials may comprise any of the following substances either alone or incombination, as will be further noted.

Oil-soluble dyestufis Dyestuffs of the types above listed are ink-recaptive and -retentive, and also spontaneously sorptive. and may be used for direct-image delineation in a solvent vehicle. Lump oil aniline black may be used for direct-image delineation without a solvent vehicle.

Gums and resin:

Gum copal Gum guaiac Gum mastic Gum shellac Gum accroides Gum olibanum Gum sandarac Gum kauri Gum elemi Abietic acid Gums and resins of the types above listed are ink-receptive and -retentive, and either are spontaneously sorptive or, as in the case of mastic, kauri and elemi, may be so modified by heating in admixture with morpholine as to become spontaneously sorptive.

Pitches, as illustrated by the coniferous, Palm 7 and linseed pitches for instance, are not in their normal semifiuid state useful for-the present purposes, but may be rendered useful for said purpose by polymerization and oxidation, as by irradiation with ultraviolet light for instance; thus, the said pitches while not satisfactory image-formers in their normal state may be used as photogenic image-formers by means of thin deposits thereof from a volatile vehicle on a cellulosic printing surface and subsequent selective irradiation thereof.

Vegetable oils such as cottonseed, rapeseed. linseed, linoleic and the like, are not imageformers in the unsaturated state but may be rendered useful as such by halogenation or irradiation and may be used in the unsaturated state as photogenic image-formers and be selectively irradiated as a thin deposit from a volatile vehicle on a cellulosic printing surface.

Synthetic resinous substances such as coumaron indene resin, chlorinated oleyl alcohol, highly chlorinated diphenyl, sucrose octa-acetate, urea formaldehyde resin of the Beetle type,

may be used alone or in a suitable vehicle de-' pending upon the desired mode of delineation.

Insoluble metal soaps, such as a copper, barium, iron or lead stearate, oleate, palmitate or the.

like, are all image formers and are particularly suitable for use as crayons or in crayon compositions. a

Waxes are useful for the present purposes mainly as viscosltyor plasticity-augmenting components of an image-forming composition; but shellac wax represents the most outstanding exception as it has been foundto be in and of itself a good image-former; while candilla (candelilla) wax, selected as representing a wax having a high acid number, when heated in admixture with morpholine has also been found to be a good image-former, and it has been found to be true of beeswax vwhen bleached and subsequently irradiated in situ as a thin solvent residue on a unified cellulosic printing surface.

To meet the variant modes of image delineation, it is often desirable to consociate an imageformer as in combination with a substance which is itself spontaneously sorptive, but need not necessarily be ink-receptive, whereby the viscosity, plasticity or internal cohesion of. the com: position is adjusted to a particular mode of image delineation. The following substances have been found useful in image-forming compositions when said substances were in consociative combination with ink-receptive and -retentive image-formers appropriately chosen from the foregoing lists.

Solids such as ethyl ortho-benzoyi benzoate, octadecyl alcohol, octadecane diol and ortho-hydroxydiphenyl, though not of and in themselves ink-receptive, have been found useful in crayon compositions comprising ink-receptive substances pont) and triacetin, though not in and of themselves ink-receptive, have been found to be useful in more or less viscous compositions comprising ink-receptive substances chosen from those hereinabove listed.

Volatile liquids such as ethylene glycol monobutyi ether and diethylene glycol monobutyl ether. though not in and of themselves ink-receptive, have been found to be useful in imageimprinting compositions comprising ink-receptive' substances listed.

Highly volatile liquids. such'as any substantially. Pure liquid solvent substance having a high vapor pressure, though not in and of themselves ink-receptive, have been found to be useful as temporary and fugitive vehicles for spontaneous- Iy-sorptive and ink-retentive or photogenicallypotential ink-retentive substances compatible with said liquids and chosen from those substances hereinabove listed for image delineation on, photosensitization of, or background stippling of a unified cellulosic printing surface.

The following formulas of image-forming compositions are illustrative of the type of consociations of ink-receptivesubstances and vehicular substances which have been successfully used in combination with unified cellulosic surfaces and which are preferred for the particular mode of delineation indicated.

Crayon formulas v 1 Grams (l) Calco oil black F4160... 5 Ethyl ortho-benzoyl benzoate 4 The melted and thoroughly mixed mass is poured into a suitable mold, and allowed to stand and Phenol .25?

chosen ,from those hereinabove Typewriter ribbon-inking compositions Grams (l) Calco oil black F4180 4 Butyl ortho-benzoyl benzoate.. 5

The mix may be eifected by heating and stirrins until uniform, in any convenient manner. Milling between tightrolls, however, is not recommended.

hesion for such ink greater than the internal cohesion of such ink, said image-former having spontaneous sorptive adhesion for unified cellulose and being sufiiciently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat orlapse of time.

5. The combination of a unified cellulosic planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesionof such ink, said image-former including an ink receptive agent and a vehicle therefor, the image-former having spontaneous sorptive adhesion for unified cellulose and being substantially free from free, fatty acid to permit spon- Grams (2) Tricresyl phosphate-..- 5

6% solution of Beeswax in a cyclic acetate (Cyclonol) Nigrosine base black. 3' Carbon black '2 The mix may be effected in any convenient manner.

- imprinting ink Ethylene glycol monobutyl ether cc- 1.5 Diethylene glycol monobutyl ether on 7.5 orange shellac grams 12.5 Calico oil black Fil60 do- 31) The mix may be elected in any convenient manner.

I am aware that, of the gums, shellac at least has been heretofore used in colloidal dispersion in an alkaline aqueous vehicle for the direct delineation of images upon metal planographic plates; and such alkaline aqueous colloidal dispersions of gums are here disclaimed.

I am also aware that certain gums and resins have been heretofore used as secondary imageformers on metal planographic plates after the original or direct-image material has been washed out" subsequent to the gumming up" of the non-printing areas of said plates; but, as it is one of the advantages of this invention that the usual gumming up" and washing ou operations as well as the consequent necessity of'replacing the "washed out original direct-imageformins material with a secondary image-former may be avoided, and that commercially acceptable editions may be obtained from the preferred spontaneously-sorptive image-forming materials originally and directly applied to, and residual on, suitable cellulosic printing surfaces. it is considered'that the image-formers heretofore used as replacement materials are, when used on and in combination with unified cellulosic surfaces and when retained as originally deposited thereon and printed directly therefrom, within the purview of this invention.

I claim:

1. An image-forming composition for inking typewriter ribbons comprising a stearate of nigrosine and butyl ortho-benzyl benzoate.

2. An image-forming crayon composition comprising a stearate of nigrosine and ethyl ortho"- benzoyl benzoate.

3. An image-forming imprinting ink composition comprising ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, orange shellac and a stearate of nigrosine.

4. The combination of a unified cellulosic planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an adtaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time.

6. In the art of planographic printirm 'employing a unified cellulosic planographic printing surface which is not substantially chemically modified by reaction of the free fatty acid component of the usual greasy image-forming material and wherein the printing life of the surface is effective only so long as the image-forming material is retained upon the image area, a

water immiscible image former preferentially wettable by lithographic printing ink and exhibiting on a unified cellulosic surface an adhesion for such ink greater than the internal cohesion of such ink, said image-former havin spontaneous sorptive adhesion for unified cellulose and being sufiiciently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith, and immediate dampening, inking and printing, without the application of heat or lapse of time.

7. A direct image-forming crayon for use on a unified cellulosic planographic printing surface, said crayon comprising waterimmiscible image-forming material preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesion of such ink, said crayon material having spontaneous sorptive adhesion for unified cellulose and being sufficiently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without .the application of heat or lapse of time.

8. The combination of a unified cellulosic planographic printing surface --water wettable and having a lateral water diffusion rate of not more than 25 millimeters in 4 hours, and a water immiscible image-former preferentially .wettable by lithographic printing ink and exhibitingan adhesion for such ink greater than the'internal cohesion of such ink, said image-former having spontaneous sorptive adhesion for unified cellulose and being sumciently free from free fattyacid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time.

9. The combination of a planographic printing surface and an initially water immiscible unsaturated organic potentially image-forming material convertible by ultra-violet irradiation into an image-former which is preferentially wettable by lithographic printing ink and exhibits a sorptive adhesion for the unified cellulosic surface and an adhesion for such ink greater than the internal cohesion of such ink, the said unified cellulosicsurface which bears the potentially image-forming material beunified cellulosic,

ing preferentially water-wettable under the dampening and inking operations of pianographic printing notwithstanding the presence of the said potentially image-forming material.

10. The combination of a unified cellulosic planographic printing surface and a water immiscible image-former including an ink receptive material and a low vapor pressure liquid vehicle therefor, said former being preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesion of such ink,,said image-former having spontaneous sorptive adhesion for unifled cellulose and being sufficiently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time.

11. A direct image-forming crayon for use on a unified cellulosic planographic printing surface, said crayon comprising water immiscible image-forming material preferentially wettable by lithographic printing ink and exhibiting on a unified cellulosic surface an adhesion for such ink greater than the internal cohesion of such ink, said crayon material having spontaneous sorptive adhesion for unified cellulose and being sufficiently free from free'fatty acid to permit spontaneous bonding with said surface by more contact therewith without the application of heat or lapse of time. the crayon containing an oil soluble dye and a solid vehicle therefor.

12. The combination of a unified cellulosic planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesion for such ink, said image-former having spontaneous sorptive adhesion for unified cellulose and being sufficiently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time, the imageformer containing an oil soluble dye and a vehicle therefor.

13. The combination of a unified cellulosic.

planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an lose and being sufficiently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time, the imageformer containing an oil soluble dye having a Nig'rosine base and a vehicle therefor.

14. The combinatiom, of aunified cellulosic planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesion of such ink, said image-former having spontaneous sorptive adhesion for unified cellulose and being sufficiently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time, the imageform-er containing an oil soluble dye comprising a stearate of Nigrosine and a vehicle therefor.

15. The combination of a unified cellulosic planographic printing surface and a water immiscible image-former preferentially wettable by lithographic printing ink and exhibiting an adhesion for such ink greater than the internal cohesion of such ink, said image-formerhaving spontaneous sorptive adhesion for unified cellulose and being sufiiciently free from free fatty acid to permit spontaneous bonding with said surface by mere contact therewith without the application of heat or lapse of time, the imageformer containing an oil soluble dye comprising Indulin base and avehicle therefor.

16. The combination of a unified cellulosic planographic printing surface and an initially water immiscible unsaturated organic potentially image-forming material, the said unified cellulosic surface which bears said material being preferentially water wettable under the dampening and inking operations of pianographic printing notwithstanding the presence of said material, said potentially image-forming material being sufilciently free from 'free fatty acid to exihibit a sorptive adhesion for said unified cellulosic surface and being convertible by ultra-violet irradiation to become preferentially wettable by lithographic printing ink and exhibit a sorptive adhesion for such unified cellulosic surface and an adhesion for such ink greater .1 than the internai cohesion of such 1111:.

WILLIAM WESCOTT. 

